Issue #23738: Document and test actual keyword parameter names

Also fix signature because os.utime(..., ns=None) is not allowed.
diff --git a/Doc/library/binascii.rst b/Doc/library/binascii.rst
index 3f7df74..e3f134b 100644
--- a/Doc/library/binascii.rst
+++ b/Doc/library/binascii.rst
@@ -59,7 +59,7 @@
    should be at most 57 to adhere to the base64 standard.
 
 
-.. function:: a2b_qp(string, header=False)
+.. function:: a2b_qp(data, header=False)
 
    Convert a block of quoted-printable data back to binary and return the binary
    data. More than one line may be passed at a time. If the optional argument